The biological pathways that mediate the association between obesity and postmenopausal breast cancer risk are unresolved, although new data suggests that altered levels of adipokines may underlie, in part, the obesity- breast cancer relationship. To further clarify their role, large epidemiologic studies with prospectively-collected serum are needed to evaluate the associations between biomarkers of obesity and cancer risk. However, current findings on adipokines and risk of postmenopausal breast cancer are conflicting, and it is plausible that major differences in blood collection protocols across studies may have contributed to this variance. Therefore, before new studies can be conducted, several methodologic/biologic issues need to be addressed. First, given their role in energy metabolism, it is possible that serum adipokine levels may vary in response to energy intake but it is unknown how the time between last meal and blood draw (fasting time) influences adipokine measurements, or how these effects may differ by body size. Second, delays in blood processing may accelerate degradation of these peptides; however, the extent of this effect is currently not known for adipokines. To investigate the effect of energy intake and specimen processing time on serum adipokine levels, we propose to measure adipokine levels in fasting and non-fasting samples, as well as in samples processed immediately and with delays, in 45 postmenopausal women. The study population has been recruited with available funds at the Center for Clinical and Translational Science (CCTS) at the Rockefeller University Hospital. The study subjects performed the following tasks in sequential order: (a) the night before the study visit, participants were instructed to fast, (b) the following morning, women arrived at the CCTS and provided a fasting blood sample after which they (c) consumed a standard research breakfast and finally, (d) provided 3 blood draws at 1, 3, and 6 hours postprandial. Blood samples were processed immediately, 24 hours, and 48 hours after blood draw to extract serum. We are requesting funds to analyze adipokine levels in these serum samples at Dr. Michael Pollak's laboratory. Analyte values from postprandial blood draws compared to those from the fasting blood draw, as well as from different processing times, will be evaluated using analysis of variance tests for repeated measures and paired t-tests. Results of this study are expected to inform future investigations of adipokines and female reproductive cancers, which involve primarily postmenopausal women, although results will be applicable to other outcomes and possibly to other groups including premenopausal women and men. Thus, we believe that understanding the role of fasting status and blood processing time in a controlled clinical setting will be critical for the design, analyses, and interpretation of large epidemiologic studies of obesity biomarkers and postmenopausal breast cancer risk. PUBLIC HEALTH RELEVANCE: PROJECT NARRATIVE The proposed study will examine whether blood collection parameters, fasting status and processing time, influence circulating levels of adipokines in a controlled feeding trial of 45 postmenopausal women. Description of the postprandial changes and effects of processing time to adipokine levels will inform the design, analysis, and interpretation of large epidemiologic studies of adipokines and obesity-related cancers.